Sweet Corn, That Home Garden Favorite For Good Nutrition and Eating Pleasure

by E. V. Wann.

E. V. Wann is Research Geneticist and Laboratory Director at the U. S. Vegetable Laboratory, Agricultural Research Service, Charleston, S.C.

Sweet corn is a common item in most American home gardens. It provides a delightful addition to everyday meals, and in season the roasting ears are enjoyed for picnics and cookouts. Since the days of the Pilgrims, corn-on-the-cob has been a popular American favorite. Sweet corn either fresh, frozen or canned may be served as a separate dish or used in succotash (an American Indian dish), custards, puddings, fritters, souffles, and stuffed peppers, or added to soups and chowders. Sweet corn may also be used in relishes and mixed pickles.

Most gardeners will regard sweet corn as an essential item in their garden and take great pride in the good nutrition and eating pleasure it affords.

Corn (Zea mays) is a member of the grass family, which includes other cereal crops such as wheat, oats, barley, sorghum, and rice. Corn is conveniently divided into six types based on its use and kernel characteristics. These are dent corn, sweet corn, popcorn, flint corn, flour corn and pod corn. They are all of the same species but differ genetically. Dent corn, sweet corn, and popcorn are the most commonly grown for their food and feed value throughout the world.

Sweet corn is believed by most authorities to have originated in North America as a mutation from field corn. The first references to sweet corn date from 1779; an 8-rowed, red-cob type called Susquehanna, or Papoon, was introduced that year near Plymouth, Mass. In Thomas Jefferson's Garden Book (1810) "shriveled corn" is mentioned, which is obviously sweet corn.

By 1828 "sugar corn" was listed in New England seed catalogs. Also, evidence indicates sweet corn was being grown by the American Indians Of the upper Missouri by 1833. Another early reference to sweet corn appeared in the Travel Letters (1821) of Timothy Dwight as being the most delicious vegetable of any known in this country.

Sweet corn as a specific crop must have come into existence at least by 1820 and reached sufficient popularity by 1828 to be in a seed catalog. The subsequent history of sweet corn is one of variety development. By 1900 there were no less than 63 varieties, and the first F, hybrid was introduced about 1924. Today, there are well over 200 varieties and hybrids available to sweet corn growers and gardeners.

Sweet corn differs from the other types of corn primarily by its ability to produce and retain greater quantities of sugar in the kernels. This characteristic is conditioned by a single recessive gene called sugary-1, symbolized su1. Other less pronounced differences are its tender kernels at edible maturity, refined flavors, a tendency to produce suckers at the base of the plant, and wrinkled seeds when dried. Dent corn is considered the "normal" type with all the other types being genetic variation (mutations) of it. Popcorn, for example, has very hard starch in the kernels that expands explosively when heated, thus producing the fluffy white popcorn kernel.

In recent years a new kind of sweet corn has come into use that is sweeter than the standard sweet corn. Its sweetness is not conditioned by the sugary-1 gene but by a similar genetic factor designated shrunken-2 (sh2). This gene conditions an even higher level in sugar in the kernels, giving them a sweeter taste and prolonging the edible state by three or four days.

Well-filled ear of sweet corn.

The different types of corn should never be planted together at the same time. Pollen from dent corn or popcorn will contaminate sweet corn, causing the kernels to be starchy and not sweet. Likewise, the standard sweet varieties should not be inter-planted at the same time with the extra sweet (shrunken-2) varieties, as the pollen from one will contaminate the other destroying the quality of both. If both types are to be planted they should be separated by at least 400 yards distance, or one planted about four weeks after the other so they are not pollinating at the same time.

Climatic Needs

Sweet corn is essentially a warm-weather crop. It is easily killed by frost and may be seriously injured by prolonged temperatures several degrees above freezing. Germination and emergence of the seedlings are delayed and may be prevented by soil temperatures below 50 F. Sweet corn does best in areas having mean temperatures of 65 to 75 during the required 65- to 100-day growing season. In the Northeast and North Central States this corresponds to the months June, July and August. In central and south Florida, on the other hand, sweet corn is planted fall, winter and spring. Generally, sweet corn can be grown successfully in the proper season from Mexico to Canada and in many other parts of the world.

Sweet corn will grow satisfactorily on a wide range of soil types as long as they are friable and well drained. However, a deep, loamy, naturally rich soil is preferred. Soil should be only moderately acid (pH 5.8 to 6.8). If the pH is lower than 5.8, lime should be applied. Have soil tests made to determine the proper kind and amount of lime and fertilizer to apply. Consult your local Agricultural Extension Agent since most States have laboratories that provide a soil testing service.

Available plant nutrients are especially important early in plant growth. If the plants become nutrient-deficient and stunted, they never fully recover and the yield will be reduced. Commercial fertilizers are recommended for sweet corn on just about all soils throughout the country. Fertilizer recommendations for sweet corn vary for different sections of the country and from one soil type to another. Again, depend on soil testing for specific recommendations.

Some general fertilizer recommendations for typical soils follow:

On light sandy soils of the Atlantic and Gulf Coastal Plains, broadcast 20 pounds of 10-10-10 fertilizer per 1,000 square feet of area before planting. Then apply a side dress of nitrogen when the corn is in the 6 to 8 leaf stage at the rate of about a half pound of actual nitrogen (N) per 100 feet of row (note that Ammonium Nitrate contains 33 percent actual N and Sodium Nitrate contains 16 percent).

On soil of average fertility in the Northeast, apply 15 to 18 pounds of 5-10-5 per 1,000 square feet of area prior to planting and about 3 pounds of the same fertilizer banded per 100 feet of row at the time of planting.

In the more fertile valleys of the West and Pacific Northwest and on the rich soils of the Midwest corn belt, apply in bands 3 to 5 pounds of 5-10-5 per 100 feet of row at the time of planting.

The broadcast applications are usually worked into the soil before planting. The band applications should be made when the seedbed is prepared, about 3 inches to the sides of the row of seed and 1 to 2 inches deeper than the seed is planted. The above rates are based on rows spaced 3 feet apart.